The present invention relates to a device for moving a fluid, with the device capable of being used in an ink jet printer.
In ink jet printing technology, the main concerns are to improve the quality as well as the speed of printing. An objective of almost all printing technologies developed at present is to produce high quality copies as fast as possible. For ink jet technologies, to achieve fast printing, various manufacturers increase the number of nozzles on the surface of the heads which are capable of ejecting ink drops in order to print a greater number of points in parallel on the receiving medium. However, the number of nozzles on the surface of the head is limited either because of problems related to heat dissipation in methods which use high temperature ink, such as in technologies developed by Canon and Hewlett Packard; or because of problems related to dimensional instability due to vibrations caused by the use of piezoelectric technologies, such as those developed by Seiko-Epson.
U.S. Pat. No. 5,612,725 discloses an ink-jet recording head whose nozzles and ink flow channels can readily be formed and thus mass produced and which uses inexpensive glass and plastic plates. Components of the ink-jet recording head are collected together by a thermal fusion bonding method which improves the quality of the assembly. Moreover, the inner faces of the through-hole and the intermediate nozzle are made hydrophilic, whereas the inner and open faces of the terminal nozzle are made water-repellent or hydrophobic. The state of faces of the components are permanently either hydrophilic or hydrophobic; the state of a given element cannot be changed from hydrophilic to hydrophobic or inversely.
One of the technologies traditionally used in ink jet heads includes raising the ink found in a channel to a high temperature in a short time, typically 300 to 400xc2x0 C. This causes local vaporization of the ink which causes the expulsion as drops of the liquid part of the ink found between the vaporization zone and the surface of the ink jet head. This method requires thermal energy in the volume of the ink jet head itself, which must then be dissipated.
Other techniques, for example those described in Pat. Application WO96/32284, includes bringing a fluid into contact with a ring shaped heating element located at the periphery of the opening of a channel linking a reservoir containing the fluid to the opening on the surface of the ink jet head. Pressure is applied to the reservoir in order to allow the ink to be sent through the channel and to spread over the heating ring surface of the ink jet head.
When the heating element of the ink jet head is raised to a temperature of about 130xc2x0 C., there are significant changes to the surface tension of the ink drop in contact with the heating element. The surface tension change causes a decrease in the radius of curvature of the ink drop meniscus thus allowing it to run freely through the channel and to form a drop of the appropriate size for the printing required. Once formed, this drop is then ejected by means that can be an electrostatic field between the ink jet head and the printing medium, for example a sheet of paper. This technique, which has the advantage of considerably lowering the temperature needed to eject a unit volume of ink, is thus more appropriate to the manufacture of highly integrated ink jet heads. However, while in theory it is necessary only to heat the surface of the ink drop meniscus to get the change in its radius of curvature and thus to get the formation of the ink drop, in practice it is necessary to heat the whole volume of the ink drop which requires a much higher energy supply to eject an ink drop. However, it should be noted that as the ink is heated in its volume, part of the energy supplied to get the ink drop is still contained in it on ejection; this makes the dissipation of this energy easier, as it does not stay confined in the ink jet head itself
An object of the present invention is to provide a device for moving a fluid, for example ink, which minimizes the amount of energy required to eject a drop of this fluid. Such a device allows a fluid to be ejected out of a channel, and allows fluid with an accurately set volume to be ejected.
The present invention relates to a device for moving a fluid. The device includes:
a) a least one polymer element having hydrophilic or hydrophobic properties, with the polymer element being in contact with said fluid; and
b) at least one stimulus element for generating an external stress on the polymer element to select hydrophilic or hydrophobic properties corresponding to two different hydrophilic or hydrophobic states of the polymer element, and thus allowing a switching of the polymer element from one state to the other.
The present invention also relates to a method for moving a fluid which involves the use of a polymer whose hydrophilic or hydrophobic properties can be selected under the action of an external stress in a device for moving this fluid.
The present invention also relates to a printing fluid jet head that includes:
a) at least one internal channel ended by a nozzle, an outflow of a printing fluid in said nozzle being directed to an outside of said fluid jet head;
b) at least one device for feeding a printing fluid through an end of the internal channel opposite to said nozzle; and
c) a device for moving the printing fluid. The device for moving the printing fluid comprises at least one polymer element having hydrophilic or hydrophobic properties. The polymer element is in contact with the printing fluid, and the hydrophilic or hydrophobic properties of the polymer element corresponds to two different hydrophilic or hydrophobic states being selected under an action of an external stress provided by at least one stimulus element.
The present invention also relates to a printing method which comprises the steps of contacting a fluid with a polymer element, with the polymer element comprising polymers whose hydrophilic or hydrophobic properties are selected under an action of an external stress; and moving the fluid by switching the polymer element between a hydrophilic state and a hydrophobic state.
The present invention also relates to a printing fluid jet head which comprises a polymer element having hydrophilic or hydrophobic properties which are selected under an action of an external stress. The polymer element is adapted to contact a fluid to be moved and move the fluid when the polymer element is switched between a hydrophilic state and a hydrophobic state.
All the embodiments of this invention, which will be described below, are used to move a hydrophilic fluid. However, when the fluid to be ejected is hydrophobic, the embodiments described below are applied using appropriate polymers. For example, polymers can be chosen which are in their hydrophobic state when they are not subject to an external stress and in their hydrophilic state when they are subject to an external stress.